Null Pointer Exception on stmt = conn.prepareStatement( query );

Question

I configured the Tomcat 5.0.27 for using the connection pool feature and connecting to the Oracle. I am testing if I did the configuration correctly. Therefore, I try to retrieve some data from a table. I got the
'Null Pointer Exception" when executing the
         stmt = conn.prepareStatement( query );I am not sure where the problem is from.
1. configuration is not done properly?
2. some bugs in my program?
I need your help to diagnose the problem. The messages in the Tomcat log are shown below my program coce.
The code for class where the 'Null Pointer Exception' occurred is like:
package org.dhsinfo.message.dao;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.PreparedStatement;
import java.sql.Statement;
import java.sql.SQLException;
import org.dhsinfo.message.MemberBean;
import org.dhsinfo.message.exceptions.MemberDAOSysException;
import org.dhsinfo.ConnectionPool.DBConnection;
public class OracleMemberDAO implements MemberDAO
   // Here the return type is Collection
   public Collection findMembers()
       throws MemberDAOSysException
      Connection conn = null;
      PreparedStatement stmt = null;
      ResultSet rs = null;
      MemberBean memberBean;
      Collection members = new ArrayList();
      String query = "SELECT name FROM PersonType";
      try
         conn = DBConnection.getDBConnection();
         stmt = conn.prepareStatement( query );  // line number 32
         rs = stmt.executeQuery();
      while( rs.next() )
         memberBean = new MemberBean();
            memberBean.setName( rs.getString( "name" ) );
         members.add( memberBean );
         return members;
      catch (SQLException se)
         se.printStackTrace( System.err );
         throw new MemberDAOSysException("SQLException: " + se.getMessage());
      finally
         if ( conn != null )
            try
               rs.close();
               rs = null;
               stmt.close();
               stmt = null;
               conn.close();
            catch( SQLException sqlEx )
               System.out.println( "Problem occurs while closing " + sqlEx );
            conn = null;
}java.lang.NullPointerException
     at org.dhsinfo.message.dao.OracleMemberDAO.findMembers(OracleMemberDAO.java:32)
     at org.dhsinfo.message.MemberService.getMembers(MemberService.java:18)
     at org.dhsinfo.message.SendMessage.execute(SendMessage.java:29)
     at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:484)
     at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:274)
     at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
     at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:525)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
     at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
     at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
     at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
     at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
     at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
     at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
     at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
     at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
     at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
     at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
     at java.lang.Thread.run(Thread.java:534)

Answer 1

Here is my DBConnection.java class. I have used it many times. I feel like going one by one. If it is not my DBConnection .java class, then the next thing to look at is my connection pool configuration. I have a feeling that it is my connection pool configuration.
package org.dhsinfo.ConnectionPool;
import java.sql.Connection;
import java.sql.SQLException;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;
public class DBConnection
   public static Connection getDBConnection() throws SQLException
      Connection conn = null;
      try
         InitialContext ctx = new InitialContext();
         DataSource ds = ( DataSource ) ctx.lookup( "java:comp/env/jdbc/OracleDB" );
         try
            conn = ds.getConnection();
         catch( SQLException e )
            System.out.println( "Open connection failure: " + e.getMessage() );
      catch( NamingException nEx )
         nEx.printStackTrace();
      return conn;
}